1. Field of the Invention
The present invention relates to a filter for removing colloidal, soluble, and insoluble materials from a fluid using an adsorbent to remove the soluble portion of the contaminant, and the addition of an electrostatic attraction additive to extract the colloidal and particulate portion of the contaminant out of the fluid, which could be held indefinitely, or at least while the contaminant is allowed to solubilize, at which point it is then removed by the adsorbent.
2. Description of Related Art
Certain water treatment applications are characterized by the need to remove both dissolved and suspended or colloidal materials. Although it has been used in numerous consumer products, toxic metals, such as lead, is known to be harmful to human health if inhaled or ingested. Important sources of toxic metal exposure include: ambient air, soil and dust (both inside and outside the home), food (which can be contaminated by toxic metals in the air or in food containers), and water (from the corrosion of plumbing). Materials such as ion exchange resins and reverse osmosis membranes effectively reduce or fully remove dissolved ionic species.
Particulate lead at high pH exists primarily as colloidal lead carbonates. These colloidal particulate solids can be physically removed if the filter media provides for a fine enough mesh that can also accommodate pressure differentials.
It is known to separate particles, such as dirt and dust particles from a fluid flow using mechanical filters, such as foam filters, cyclonic separators, and electrostatic separators where dust particles are charged and then attracted to another oppositely charged surface for collection. This is the common use of electrostatic filters.
Known electrostatic filters include factional electrostatic filters and electret medium filters. Examples of such filters are described in EP 0815788, U.S. Pat. Nos. 7,179,314, and 6,482,252.
Electrostatic filters are commonly used for air filtration. In typical electrostatic filter operation, a safe static charge is produced by forcing air across the filter. This static charge attracts and traps airborne particles into the filter. Electrostatic air filters generally work by sieving materials via fibers that are designed such that when air flows through them they acquire static charges. Other fibers acquire negative charges and the charges draw materials in a similar fashion as being drawn by magnets. Afterwards, filtration takes place leaving the materials on the surface of the filter.
In an alternative embodiment to mechanical filters for fine particle filtration of fluids, including dielectric fluids, fluid is made to pass through a number of electrodes which are alternately charged with relatively high positive and negative voltages. Porous filter material is placed between the electrodes for trapping the particulates. Particulates, when subjected to the electric fields created by the application of voltage to the electrodes, are filtered in one of two possible ways. The filter material itself may be charged with the particulates being attracted to the filter material itself. More likely, however, the particulates are charged, either positively or negatively, depending on their composition, and the oppositely charged particles will be attracted to each other and eventually form larger particulate clusters which will be large enough to be trapped in the filter material. Whenever enough clusters form to effectively block the filter, or produce an undesirable pressure drop, the filter must be replaced.
Although electrostatic filters have been known in the art for some time for air filtration, there remains a need in the art for improved filtration regarding the removal of soluble and colloidal, non-soluble particles in a fluid, and untested at present, electrostatic filters may play a role in this removal.